Electric clock system



' June 24, i930 H. E, WARREN 1,7 7,949

'ELECTRIC CLOCK SYSTEM Orig-inal Filed Jan. 24, 1928 Inventor: Henry E.WaYren. 166* Patented June 24, 1930 UNITED STATES PATENT OFFICE HENRY E.WARREN, OF ASHLAND, MASSACHUSETTS, ASSIGNOR TO WARREN TELE- CHRONCOMPANY, OF ASHLAND, MASSACHUSETTS, A CORPORATION OF MAINE ELECTRICCLOCK SYSTEM Original application filed January 24,

My invention relates to electric clock systems in which one or moresecondary clocks are driven by synchronous motors connected to a sourceof alternating current. More particularly my invention relates to animproved method and apparatus for resetting the secondary clocks afteran appreciable interruption in the current supply. This application is adivision of my application, Serial No. 249,175, filed January 24, 1928,assigned to the same assignee as the present invention.

In electric clock systems it is desirable that each secondary clockindicate correct time. If these clocks are driven by synchronous motorstheir rate is directly proportional to the frequency of the alternatingcurrent supply and the time indicated is correct only if the frequencyhas remained constant at the value for which the clock gearingisdesigned and if the current has not been interrupted.

.By means of improved regulating and generating equipment it is nowpossible to maintain substantially constant frequency on commercialpower systems. Interruptions in service, however, due to lightning,short circuits and'other causes well known to those skilled in the artare practically unavoidable. It is, therefore, desirable to equipelectric clock installations with means for quickly setting thesecondary clocks, as soon as cur rent is again available, after aninterruption.

The primary object of my invention to provide simple and I eiiicientapparatus for temporarily increasing the speed of the secondary clocks,after every appreciable interruption in service, until they againindicate correct time.

The features of my invention which are beiieved to be novel andpatentable are set forth in the appended claims. My invention both as toits organization and method of opera tion together with further objectsand ad vantages thereof, will best be 1 rstood by reference to thefollowing des in connection with the accom w ings in which Figs. 1 and 2are it and side views respectively, of the resetting device; Fig. 3 is adetail view of part shown in Figs. 1 and 2; Fig. 4; is a schematicdiagram 1928, Serial No. 249,175. Divided and this application filedJune 4, 1929. Serial No. 368,270.

of an electric clock system equipped with my resetting mechanism.

Figs. 1 and 2 show the resetting control device comprising a springoperated clock mechanism, used as a master clock or timing device,arranged to be bodily rotated by a motor, a pointer operated by theclock and a switch actuated by the pointer. Referring to these figuresmore in detail, 10 indicates a standard marine clock movement supportedbetween plates 11 and 12. All details of this movement are not shown.The main driving spring is located inside of drum 13 and is wound bymeans of shaft 14 extending through plate 12. A gear 15 is rigidlymounted on the end of this shaft. The minute hand shaft 16 alsoextendsthrough plate 12 and operates a pointer 17 and pinion 18. The clockmovement 10 is mounted on a large gear 19, so that the axis of theminute shaft is in alignment with the center of the gear. On the otherside of the gear 19, extending perpendicularly to it, a sleeve 20 isprovided whose axis is also in line with the center of the gear. It isfitted loosely over shaft 21 which in turn is rigidly mounted on baseplate 22. The entire clock movement may thus be rotated as a unit, aboutan axis which coincides with the axis of the minute shaft. Sleeve 20 isheld in. place over shaft 21 by screw 23 upon which a pinion is rigidlymounted. lVhen gear 19 rotates, a gear 25 engaging this stationarypinion 24., is retated and drives a pinion 27 by means of shaft 26extending through plates 11 and 12. The pinion 27 engages gear 15 anddrives shaft 1 1, thus Winding the spring. T tin of gears is soproportioned that norm spring is wound at the same rate that it unwinds,whereby it is maintained at constant tension.

Gear 19 is arranged to be driven countem clockwise by a motor 28 througha set of reducing gears. The motor is preferably of the self-startingsynchronous type such as isdescribed in my Patents 1,288,482, 1,283,434and 1,283,435. Motor 28 drives gear 19 at a normal rate of onerevolution per hour by means of gear 29 mounted on its shaft andengaging gear 30. Gear drives a pinion 31 engaging gear 19.

Pointer 17 is operatedclockwise by the master clock mechanism at therate of one revolution per hour thus corresponding to the minute hand ofa clock. During normal operation of motor 28 this, pointer, therefore,remains stationary at any predetermined position. But when motor 28 sto5 due to an interruption in service pointer 1 will immediately moveclockwise. The angular distance that it moves from its normal positionis, therefore, a measure or integration of the interruption of serviceor of the negative frequency error and if the motors of the secondaryclocks stopped at the same time, this distance is also equal orproportional to that which the minute hands of these clocks should beset ahead to indicate correct time. Therefore, in order that theposition of this pointer 1! may control the resetting of the secondaryclocks I cause it to actuate a switch as hereinafter described inconnection with Fig. 4, and I connect the motor of this resetting deviceto the source from which the secondary clock motors are energized.

Fig. 4 illustrates diagrammatically an electric clock system equippedwith a resetting device such as illustrated and described in connectionwith Figs. 1 and 2. The secondary clocks are each operated by a.synchronous motor of which only the connections are indicated, which 0erate the clocks throu h a gear transmiss1on, not shown.

Re erring now in detail to this figure, 32 and 33 indicate the incominglines from any suitable commercial source of alternating current. Thesecondary clocks are indicated at 34 and are connected in parallel tothe buses 35 and 36. Bus 35 is connected directly to line 32 and bus 36,as well as one terminal of motor 28 are connected to line 33 through aswitch 37. Switch 37 under normal conditions is biased against contact38 by spring 39, and thereby connects motor 28 and the secondary clocksto the source 3233. During resetting operation however, it is biased toconnect the motor 28 and the secondary clock motors to a higherfrequency source. v a

The position of the switch is determined and controlled by the resettinmechanism through pointer 17. Pointer 1 engages at its end a contactspring 40, which is electrically connected to one end of a magnet coil41 which when energized closes a switch 42. Contact spring is so mountedbetween two adjustable contact posts 43 and 44 that it may be forcedinto contact with post 44 by pointer 17, butengages contact 43 ifreleased. Contact post 44 is connected to conductor 35, and 43 isconnected to contact 45 of a thermostatic switch 46. When theinstallation of the resetting device is made, pointer 17 is set toforcecontact spring 40 in engagement with contact post 44. This positionis maintained, as has already been explained, as long as motor 28 isenergized and operates. As soon as motor 28 is deenergized and stops,pointer 17 will move clockwise due to the o eration of the clockmechanism and there y releases contact spring 40 which then makescontact with contact post 43. An electric circuit is thereby establishedfrom line 32 through 35 to which one end of magnet coil 41 is connected,through coil 41, spring '40, contacts 43 to contact 45 of switch 46.Switch 46 is a thermostatic element heated by a coil 47 connected to thecommon source. The circuit is, line 33, conductors 48 and 49, coil 47,reactance 50, conductor 35 to line 32. When coil 47' is deenergizedthermostat 46 cools and flexes toward contact 45. The time that 46 takesto cool and engage contact 45 can be adjusted to any suitable value andconstitutes the shortest time for which resetting is desired. The

switch 46 is not essential and may be omitted in which case 43 will beconnected directly to line 48. Switch 46 is employed to prevent frequentoperations of the clock resetting device due to slight variations in thenormal frequency supply and failures of only momentary duration. Whenthe clock system is connected to an unregulated source it is advisableto omit this switch 46 soas to allow resetting dueto frequency errorsonly.

When in the case of a service interruption 46 cools and engages contact45, a circuit is established which connects magnet coil 41 to the powersource. This circuit is from line 32, conductor 35, coil 41, spring 40,contacts 43 and 45, thermostat 46, conductor 49 to which it iselectrically connected, to conductor 48 and line 33. When power is againavailable coil 41 will be energized and will close switch 42 against theaction of a spring. This closing of switch 42 ener 'zes motor 51 of thefrequency converter. he circuit is line 33, conductor 48, switch 42,motor 51, conductor 35 to line 32. This motor then starts and drivesgenerator 52. When this generator builds up its voltage, a magnet' coil53 connected across its terminals is energized and actuates switch 54.Switch 37 is a double throw switch which, when coil 53 is deenergized,is held against contact 38 by the action of spring 39, thereby causingmotor 28 and the secondary clock motor to be energized from the lines3233. When coil 53 is energized, 37 makes contact with contact 54 whichis connected to one terminal of the generator. The other terminal of thegenerator is permanently connected to one terminal of the clock motorsand motor 28, through conductor 35. The motor 28 and the clock motorsare therefore supplied by this generator duri nod. The frequency of t 'scurrent is prefthe resetting pehas a ain reached its normal position.When switc 42 opens, it opens the circuit to the motor of the frequencyconverter which stops. As soon as generator 52 stops coil 53 isdeenergized, switch 37 opens and connects motor 28 and the secondaryclock inotors to the commercial source whereupon normal operation isresumed.

Fig. 3 shows an attachment to the resetting device shown in Figs. 1 and2 to take care of an interruption in service lasting longer than onehour. It is evident that if power is off more than one hour the pointer17 will have made one complete revolution and would under normalconditions engage contact spring on its reverse side, thereby breakingor otherwise becomingdamag ed. To avoid this I provide gear 55 suitablysupported on base 22 by means of studs 56, cross piece 57 and pin 58, toengage pinion 18. This gear-55 is provided with a projecting cam surface59 comprising eleven twelfths of a complete circle, and is set so thatthe pointer 17 touches,

the gear surface at a point between the ends of this cam surface 59 whenit is in its normal position. The ratio of the pinion to the gear is 1to 12, so that when pointer 17 and pinion 18 have made one revolution,the gear 55 has made one twelfth of a revolution and has interposed camsurface 59 between itself and the pointer. As the pointer then returnsto engage spring 40 it engages cam surface 59 and is thereby deflectedrearwardly so as to pass contact spring 40. This same action takes placefor twelve consecutive'revolutions of pointer 17, if the power isoffthat long. After the twelfth revolution, however, the open space betweentheends of the cam surface 59 is again in such position that if power,

were turned on at that moment the pointer would. be in its normalposition and no resetting would take place. 7 If the power is off lessthan twelve hours and more than one, the cam surface 59 also preventsthe engagement of pointer 17 with spring 40- on its return journeuntilthe correct hour is reached.

In accor ance with the provisions of the patent statutes, I havedescribed the princionly illustrative and that the invention can ple ofoperation of my invention, to ther with the apparatus which I now consier the best embodiment-thereof; but I desire to have it understood thatthe apparatus shown s be carriedoutby other means. a

What I claim as new and desire to secure v by Letters Patent of theUnited States, i S,-

1. In an electric clock system connected a source of commercialalternating current, secondary clocks operated b gynchronous motors, asecond source of a ternatmg current havin a f uenc ater than the firstdme a ii s for cgiiiiecting said clock source, an

system to said high frequency sourceto correct for the negativefrequency error of the first source, including a master clock providedwith a minute hand, means to rotate.

said master clock in synchronism with, but in opposite direction to, thesecondary clock minute hand and provided with a switch controlled bysaid master. minute hand and arranged to connect said clock system toeither of said two sources.

2. An electric-clock system including secondary clocks operated bysynchronous motors, a resetting device including a spring operatedmaster clock provided with a minute hand, a synchronous motor arrangedto rotate said master clock in synchronism with the minute hands of saidsecondary clocks but in opposite direction thereto, a commercial sourceof alternating current, a secondary source of alternating current havinga frequency higher than that of said'commercial source and a switchcontrolled by the minute hand of said master clock arranged toconnectsaid system to either of said two sources.

3. An electric clock system including secondary clocks operatedby'synchronous motors, a resetting device including a spr ng operatedmaster clock provided with a minute hand, a synchronous motor arrangedto rotate said master clock in synchronism with the minute hands of,said secondary clocks but in opposite direction thereto, a commercialsource of alternating current, a second source of alternating; currenthaving a frequency higher than that of said commerclal source, a switchcontrolled by said master clock minute hand arranged normally to connectsaid system to said commercial source, and means to connect said systemto said second source to eliminate the negative frequency error of saidfirst source, and means In witness whereof I have hereunto set my I hdth' 31st da of May 1929.

9 1S ENRYEJWARREN.

